The objective of this work is to describe in detail the structure- function biochemistry of bacterial neuraminidases. The immediate goal is to complete an ongoing survey of affinity chromatography as a means to permit the facile isolation of homogeneous neuraminidase from Diplococcus pneumoniae and other microbial enzyme sources. The availability of homogeneous enzyme will permit refinement of the characterization of pneumococcal isozymes by determining such physical and chemical parameters as molecular weight, C- and N-terminal amino acids, and carbohydrate location on the protein chain. The mechanism of action of this enzyme will be investigated by determining the amino acid residues at the active site by the use of conventional group-specific and site-directing irreversible inhibitors. The latter compounds may have potential chemo-therapeutic value in the treatment of such infectious diseases as influenza and bacterial pneumonia. The question of whether the isozymes of neuraminidase are of physiological significance to the pneumococcus, or whether these multiple forms represent modification of a presumptive parental intracellular enzyme, will be further studied. A corollary objective is the preparation of immobilized neuraminidases and comparison of their physical and chemical properties to those of the free species. Such immobilized preparations offer the potential, in parallel with the homogeneous unbound enzyme, in applicability as probes to further elucidate the role of sialic acid in cell membranes of normal and malignant cells.